I feel this is comparing apple and pears. For sure AWS is more expensive, however, you looking at a markup of 50%, at most 100%.
For sure Cloud is more expensive, but if you quote 500%, you are overlooking hidden costs.
For sure Cloud is more expensive, as it charges a premium for not having to invest upfront in a lot of hardware, however,if it was 1000% no one would be using the Cloud.
I have a fixed day or two each year working out what to buy and getting quotes (which would be the same time whether it's 20 or 200 servers), half a day per 20 servers for installation in racks, and call it half a day per 20 for initial configuration (most of the time to script the process, so it would also be similar for 200). After that, it's at absolute most an hour every couple of months to deal with a failed disc or similar.